WASHINGTON (CNN) -- Socks, the cat who won international fame during his years in the Clinton White House, was euthanized Friday after months of treatment for cancer.

Socks, who was born in 1989, was put to sleep about 10 a.m. at Three Notch Veterinary Clinic in Hollywood, Maryland, said veterinary assistant Rae Dera. Veterinarians say he was probably either 19 or 20 years old.

The cat had been losing weight since November and had been treated at the clinic, Dera said. He had been suffering from a cancer in his mouth and jaw.

Since the Clintons left the White House in 2001, Socks had lived with Betty Currie, former President Bill Clinton's secretary. The Clintons were known to have visited Socks, and Currie, when in Washington.

He had been a stray and was adopted by Chelsea Clinton, the Clintons' daughter, when Bill Clinton was governor of Arkansas.

"Socks brought much happiness to Chelsea and us over the years, and enjoyment to kids and cat lovers everywhere," Bill and Hillary Clinton said in a joint statement released by the William J. Clinton Foundation. "We're grateful for those memories, and we especially want to thank our good friend, Betty Currie, for taking such loving care of Socks for so many years."

The black-and-white feline was a fixture at the White House during the Clintons' eight-year run. He was often photographed on the president's shoulder and was given free rein of the presidential residence -- showing up in photos in the Oval Office and White House press briefing room.

He had his own online fan club, appeared at animal charity events and was one of the subjects of now-Secretary of State Hillary Clinton's book, "Dear Socks, Dear Buddy: Kids' Letters to the First Pets."

"Remember - every time your dog gets somewhere on a tight leash *a fairy dies and it's all your fault.* Think of the fairies." http://www.positivepetzine.com"

Run Hard at the Rainbow Bridge My Angel Sock-M! I Love You Baby Girl! Now that your Mom Starlit is up there too, please help her learn the ropes, love and keep her company until I can see you both again. Starlit I love you!http://i14.tinypic.com/2a8q345.jpg